1. The Field of the Invention
The present invention relates to tailings disposal in minerals processes, more particularly to a system of disposal that increases the geotechnical stability of the material for disposal, and most particularly to unique combinations of fine tailings streams and coarse tailings streams.
2. The Relevant Technology
Minerals processes often produce tailings: waste material that often needs to be disposed of. Minerals processes may include coal production, fertilizer production, base metals production, copper ore production, gold production, rare earth production, industrial minerals production, iron ore production or other similar processes. These processes can often produce waste material such as overburden, waste rock, and tailings that are coarse and fine. These processes may also require the disposal of tailings, which may be difficult given that fine tailings often retain moisture for an extended amount of time, even years, without treatment, and often must be kept in tailings ponds until they can become geotechnically stable materials. Geotechnical stability is often required for reclamation, but not necessarily to the stability level that may be required for underground paste-backfill operations in which Portland cement, other fixation chemicals such as lime, or geopolymers may be added to waste material to achieve a concrete type solid material.
Fine tailings streams often comprise water. This water may be difficult to reclaim or extract from a fine tailings stream due to the very small sized particles prevalent within that stream. Natural, unforced evaporation of the water from the fine tailings streams is often a very long process and usually not feasible given acreage constraints frequently encountered at minerals processing plants. Filters may be used to remove water from the fine tailings streams. However, these dewatering apparatus often have a high relative capital equipment, expenditure, and operational costs and are often very large due to the amount of water in the fine tailings streams. Small particle sizes may further complicate the dewatering process. Dewatering for water recovery becomes more and more necessary, particularly in arid climates where water costs are significant. Additionally, dewatering may reduce time in tailings ponds and may aid plant managers in reaching their goal of turning tailings into geotechnically stable land.
Coarse tailings, as well as overburden and waste rock, are also often produced in minerals processing. These materials can be large in size and are often easily disposed of on disposal piles. Some have thought to combine the coarse tailings with the fine tailings on disposal piles, but the resultant permeability due to the discrepancy in average size between the particles from fine tailings and the particles from coarse tailings leads to a mixture that may wash away and is often far from geotechnical stability.